Bearing



1950 V w. ,1. PARKS 2,532,327

BEARING Filed June 26, 1948 6 Sheets-Sheet 1 INVE R. WALTER J. PA

BY j'aa jfy ATTORNEY-9 Dec. 5,, 1950 w. PARKS 2,532,327

BEARING 6 Sheets-Sheet 3 Filed June 26, 1948 IN E 'EN TOR. WALTER J PAR/f8 ATTORNEY-S Dec. 5, 1950 w. J. PARKS BEARING Filed June 26, 1948 6 Sheets-Sheet 4 L), Jowf' ifs ATTOENEYS Dec. 5,' 1950 w. J. PARKS 2,532,327

BEARING Filed June 26, 1948 6 Sheets-Sheet 5 INVENTOR. WALTER J. PAR/(S Dec. 5, 1950 w. J. PARKS 2,532,327

BEARING Filed June 26, 1948 6 Sheets-Sheet 6 IN VEN TOR. MLTEB J PAR/(S Patented Dec. 5, 1950 UNITED STATES PATENT- OFFICE BEARING Walter J. Parks, Aurora, Ohio Application June 26, 1948, Serial No. 35,433

8 Claims. 1 a

The present invention, relating as indicated to a bearing mounting structure and method of forming the same, is more particularly directed to the provision of a structure or unit for use with either sleeve or anti-friction bearings and which will simplify the installation of the hearing elements either into a housing or onto a shaft and at the same time eliminate some of the precision workmanship now necessary on the parts in which or on which the bearing is mounted. The mounting structure also provides a definite means permitting the bearin to align itself laterally, that is axially with respect to the location of the inner race on the shaft and the outer race in its housing, for example, so that undue axial thrust loads will not cause an overloaded condition and produce rapid failure of the bearing. The present application is a continuation-in-part of application Serial No. 759,071 filed July 5, 1947, now abandoned.

In anti-friction bearings, and particularly the ball or roller types in which both radial and axial loads are carried by the bearing, it is frequently possible, if the bearing is fitted too tightly in its supporting housing, to produce in an axial direction extraordinary pressures between the races and the balls or rollers, resulting a bearing mounting unit which can be used with in overheating, increased frictional resistance and sometimes in rapid destruction of the bearings. The final result of such diificulty is, of course, the failure of the bearing and consequently the rendering of the entire machine in which the bearing is mounted unfit for service until the bearing is replaced. An object of the present invention is to provide a mounting structure for bearings which will permit axial movement of the bearing relative to its supporting housing or member responsive to axial thrusts on the hearing before such thrust pressures deleteriously affect the bearing while at the same time providing a relatively rigid resistance to radial movement of the bearing relative to its support.

A further purpose served by the present invention is to prevent turning of the race on its mating part, that is the outer race with respect to the housing or the inner race with respect to the shaft due to any loose fit which might otherwise be necessary in order to permit the axial of axial flexibility which will permit the use of two or more bearings between a housing and shaft which shall be capable of accommodating standard bearings for providing axial displacement of the bearings relative to their support to relieve excessive axial thrust loads.

A still further object of the invention is to provide a method of form g a bearing mounting unit which is economical and which will be efficient in operation.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims; the annexed drawings and the following description setting forth in detail certain structure embodying the invention, such disclosed means constituting, however, but one of various structural forms in which the principle of the invention may be used.

In said annexed drawings:

Fig. 1 is a longitudinal central section through an anti-friction bearing and housing therefor, embodying therein my improved mounting;

Fig. 2 is a section on the line 2-2 of Fig. 1;

Fig. 3 is a partial enlarged and simplified transverse section through the housing mounting member and a portion of the bearing showing the same under axial displacement;

Fig. 4 is a transverse central section through the outer race of an anti-friction bearing, the mounting element and an outer collar;

Fig. 5 is an end view of the mounting of Fig. 4;

Fig. 6 is a partial central transverse section showinga modified form of outer collar and inner collar of a mounting unit with the mounting element interposed and secured therebetween;

Fig. 7 is a similar view of a further modification of the mounting unit;

Figs. 8 and 9 are similar views of a further modification, Fig. 8 showing the assembly in normal position and Fig. 9 in displaced relationship between inner and outer members;

Figs. 10 and 11 are similar views showing further modifications;

Figs. 12 and 13 are similar views showing other modifications of the present invention;

Fig. 14 is an end view of the device of Fig. 11;

Fig. 15 is a complete central transverse secin a double roller bearing construction;

Fig. 18 is a longitudinal section showing my invention applied to a sleeve bearing;

Fig. 19 is a similar view showing the same under uneven loading;

Figs. 20 and 21 are end elevations of two different forms of coils;

Fig. 22 is a section of the device of Fig. 21 on the line 22-22;

Fig. 23 is an end view in elevation of another form of a mounting unit which may be used to mount an anti-friction bearing in its housing, for example;

Fig. 24 is a view in section taken on line 2424 of Fig. 23;

Fig. 25 is a fragmentary top view of the outer shell of the unit shown in Fig. 23;

Fig. 26 is a view in section taken on line 2626 of Fig. 25;

. Fig. 2'7 is a view in section of a form of bearing mounting unit similar to the unit shown in Fig. 23 but showing the unit in the process of being fabricated;

Fig. 28 is a. fragmentary top view of the mounting unit shown in Fig. 27; and

Fig. 29 is a side view of a liner strip used in the fabrication of the mounting units shown in Figs. 23 and 27.

The present invention in its simplest form is shown in Figs. 3, 4, 5, 18 and 19. In these figures there is an outer collar l and an inner collar or annulus H which, in a basic form, can

. represent or constitute the outer race of an antifriction bearing assembly of which the inner race and the anti-friction members are not shown. In the case of a sleeve bearing (as in Figs. 18 and 19) the inner surface of member II is the bearing itself and the terms bearing element or inner race as used herein are intended toinclude asleeve bearing and/ or an inner race member. Interposed more or less compactiy between spaced concentric inner and outer elements [0 and II is a coil [2 of thin strip in the nature of a ribbon, usually of metal, wound about the inner memher I I to the desired thickness to be tightly fitted into the outer element I0 so that the three members when so assembled represent a unit capable of being handled, shipped and assembled without accidental disasssembly and in which the intermediate coil I2 forms substantially a solid element or body (viewed radially) between the members and H. At its outer end the coil of ribbon 12 may be secured to the member ID and may, at its inner end, be secured to the member H, although in many cases it is sufficient to rely on a roughened surface to fix the coil.

This unit as thus described forms the basis for the various adaptations and assemblies herein shown for use with various types of anti-friction bearings and may be manufactured as a unit and subsequently assemlmed with the anti-friction elements themselves and the inner race. It constitutes a secure element interposed between outer and inner elements and is capable of practically no radial yield. The only possible radial y;eld is very slight and it can be at best only a small amount depending upon a further reduction of the clearances between the laminations which have already been assembed in surface to surface contact. This is controlled by the selection of material, which is substantially incompressible,

the tightness of winding and the lubrication between the convolutions or on the surface of the same.

The principal resistance to axial displacement of the associated parts is the friction between the surfaces of the coils which friction can be controlled within definite limits by the same structural features named above, and held within the thrust capacity of the bearing. Thus element [2 permits axial displacement between elements I0 and II, in the manner shown, for example, in Fig. 3 in which the element H and the element III, while still substantially concentric with respect to each other, are displaced under operating loads by a substantial axial distance. This axial flexibility between the bearing proper and the housing permits the bearing to move axially with respect to the housing and prevents the localizing of extremely high pressures, thrust or otherwise, in the bearing caused by either improper tolerances in the manufacture of the parts, or irregularities which manifest themselves due to temperature or other conditions.

The action of the coil I2 under unequally distributed radial load, due to misassembly, misalignment, inaccuracy of manufacture or the like, is shown in Fig. 19 in which the portion of the coil most heavily loaded (the left side) is compressed and the other portion remains either as wound or is oppositely displaced. This distortion of the coil shown would necessarily be grossly exaggerated for the actual conditions inasmuch as any relative movement of opposite sides of the coil can my be to the very slight extent that the load further reduces the minute clearances between the surfaces of the convolutions which are continuously in surface to surface contact, the incompressible nature of the material composing the coil preventing any other type of displacement. The action of the coil when displaced under axial pressure will be for the convolutions to move upon themselves to permit either the housing or the outer bearing race to move axially with respect to each other by movement of the convolutions of the coil over each other through an amount required for this displacement. This action is a re atively permanent displacement, the friction between the coil convolutions being suflicient to maintain the coil in this displaced condition until some force opposite in directlon to the original displacing force acts upon it to return the coil to its original condition. In this respect the coil which represents the mounting or the interposed element between housing and race member is totally different in its action from the ordinary coiled spring or rubber-like element since in both of these cases there is within the element itself a returning force equal to the force which causes the original axial dispaoement of the element and which acts as a constant and continuing force on the bearing element.

Radially, the characteristics of the element are different from the aforementioned resilient elements inasmuch as there is substantially no radial displacement, the elements themselves being of rigid material will be in substantially surface to surface relation and act as a solid rigid element or body permitting no distortion. A further distinction between the present element and the rubber-like block employed in a similar relationship is that a rubber-like block is a monolithic structure having a definite relationship governing displacement in complementary directions depending upon the amount of rubber acted upon by radial or axial pressure while in the present element there is a very considerable axial displacement possible and practically no radial displacement and there is no structural relation between the two.

In Fig. 1 there is shown the installation of a bearing in conjunction with the present inventlon within a conventional housing in which the housing 13 is provided with an enlarged portion l4 within which is received the spiral coil l2, while within the coil l2 in turn is mounted the outer race l5, anti-friction elements l6 and the inner race ll of an anti-friction bearing construction. The inner race I1 is, of course, fitted over and is secured to the shaft l8 and is locked thereon by means of a suitable nut I9, or other suitable fastening means. On the open end of the enlarged portion l4 of the housing is a flange 20 suitably secured thereto by bolts 2i and complementing the inner portion 22 of the housing enlargement, these two portions, 20 and 22, being spaced from the convolutions of the coil l2 except at their extreme outer circumference where they engage against the outermost one or more of convolutions of the element l2.

Various modifications of the present construction may be employed, such for example as those shown in Figs. 6 to 16. In Fig. 6 there are outer and inner members 22 and 23 of unequal width, with the outer member having flanges 2d overlapping the flanges 25 of the inner member with the coil welded at its ends at the points 26 and 21 to the members 22 and 23 respectively.

In Fig. 7 there is shown an outer collar 30 and inner collar 3| and an interposed coil 32. The coil 32 is substantially the coil l2 of the figures already described. This coil is mounted within an encircling recess 33 in the member 3i and is located on the outer member 30 by means of split snap rings 35. In this assembly the action is exactly that already described, that is the interposed coil 32 acts as a nearly rigid radial intermediate member between the outer and inner elements 30 and 3| while permitting longitudinal axial displacement of these two members in either direction with respect toeach other.

In Figs. 8 and 9 I-have shown a similar construction in which, however, the coil 32 interposed between outer member 35 and inner member 36 is partially restrained from axial movealigned relation as they are displaced axially with respect to each other and also causing a return of the entire assembly to the original relationship when acted upon by a load similar 6 ations where relatively long races were required or where two or more bearings would be employed side by side to carry an extremely heavy load. In this case the coils 42 could be alter nately reversely wound regardless of the number of coils employed, which would produce a more uniform action in the entire assembly.

The structure shown in Figs. 11 and 14 comprises an outer collar 44 and an inner collar 45 with a coil 46 compacted therebetween, which coil is similar to coil l2 but it is tapered in width from-the outside to inside to a narrower central portion and the coil is maintained. in place by arcuate spring clips 41. The clips 41 have their ends in grooves 48 and 49 formed in collars 45 and 44, respectively, and the ends are pivin the opposing faces of the inner and outer:

races so that each portion of the outer race is individually loaded radially by its respective set of balls. In this assembly the two outer races 50 mounted side by side are again mounted within an outer element or housing 54 by means of the interposition between the element 54 and two outer races 50 of two coils 55, each of which is retained in position by means of springs or snap rings 58 mounted against the edges of the coils. The use of separate outer races in connection with my invention permits of a more even distribution of the load than in conven tional bearing assemblies, while permitting necessary automatic axial adjustment as required.

In Fig. 13 I have shown substantially the same constructions as in Fig. 12 except that in Fig. 13 there is an outer race 10, an inner race II, intermediate anti-frict'fon elements in the form of balls 12, and a second inner member 13 adapted to be mounted upon and about'the shaft and secured to the inner member H by means of a coil 14 which, in this connection, extends the entire axial length of the assembly instead of i be either the housing proper or an element adapted to be fitted into a housing. This element 83 is provided with two spaced, parallel circumferential pockets 84 in which are mounted coils 85 secured at their inner end to the member BI, said coils being reversely wound and having their outer ends yieldingly secured in the member 83, so that any tendency of the race 8| to rotate in either direction is at once resisted by the drawing of the free end of one coil into the space Within the member 83, producing an enlargement of the coil and a tightening of the same within the element.

In Fig. 17 there is shown a construction adapted to both mount and support the shaft 85 by means of two spaced anti-friction bearings 86 and 81, which are in turn mounted within a amass? single outer element 88 having length equal to the combined axial widths of the two bearings and the space therebetween. This entire assembly in turn then is mounted within a coil 89 which in turn is secured within a sleeve 90, the sleeve being mounted within an outer housing 9|. In such a construction not only is provision made for each of the two bearing mountings or assemblies separately but the coil 89 also acts as an equalizing device, equalizing load distribution between two spaced bearings.

In Fig. 15 I have shown a typical assembly for heavy duty operation of a pair of double bearings, each of the types capable of resisting both radial and axial loads combined in a single housing and supporting and journalling the shaft I00. Mounted about the shaft I in spaced relation are inner races ID! of the two bearing assemblies.

Operating on the outer faces of these races are two pair of angularly related rollers I02, separated by an intermediate element I03 and operating on their outer faces against a properly curved inner face I04 of two outer race members I05. The inner races are maintained in position by means of intermediate spaced rings I06, the inner ring being mounted between the two inner races and the outer ring being mounted between two outer elements I01 which are in turn secured to the outer races I05 by coils I00. This entire assembly is fitted within a housing I09 and secured therein by means of a face plate 0 held in position by means of bolts I I I.

In Fig. I have shown a coil I of tightly wound metallic ribbon having its outer and inner ends bonded to the contacting surfaces of the next adjacent convolution by welding, soldering, braz'ng or the like. A convenient method for fixing these ends is to apply a short length of fine copper wire between each end and the next adjacent convolution and then inductively heating the inner and outer convolutions brieflyto melt and flow the copper and braze the desired parts together while, of course, maintaining the coil under a circumferential pressure.

In Fig. 21 I have shown a coil I having its outer several convolutions and also its inner convolutions integrally brazed or welded together to form rigid collars of substantial thickness on the outside and inside of the coil. These joined convolutions forming the outer and inner collars may then be, and in Figs. 21 and 22 have been, finished by machining, grinding, boring, etc., so they are in concentric relation without however changing the characteristics of the 'other unsecured layers of the coil which make up the greater part thereof.

Another form of the inventr'on is shown in Figs. 23 to 29, in which I have shown bearing mounting unit 200 which consists of inner and outer cylindrical shells 20| and 202 having a coil of metallic ribbon 203 compacted therebetween. This ribbon may be of high carbon, blue steel having a fine coating of graphite on the surfaces. In this form of the invention the shells MI and 202 are formed of relatively light gage material so that by wind-- ing the ribbon 203 upon the inner shell a sufficient amount of the ribbon is interposed between the shells to cause contraction of the inner shell and expansion of the outer shell within the limits of. elasticity of the shells whereby the shells maintain compression on the coiled ribbon at all times.

In this form of the invention the shells may be formed of sheet metal stampings having downturned flanges 205 and 206 and upturned flanges 2.01 and 200. respectively. In order to cause uniattached tdsrespective surfaces of the shells as by rivets or welding, the adjacent ends of which strip being spaced apart slightly.

In making up the mounting unit .200 the shell MI is mounted on the rotatable hub of a winding device and the outer shell 202 is held stationary in a suitable fixture. The flanges 206 and 201 are notched for attaching the shells to the hub and fixture, respectively. The outer shell is provided with a slot through which the ribbon 203 is extended and this slot may be formed by cutting a tongue 2 I2 in the outer shell and bending the tongue outwardly, as shown in Fig. 26, or the slot may be formed by cutting a, diagonal opening in the outer shell as indicated in 2|2a in Figs. 27 and 28. The end of the ribbon 203 inserted between the shells is secured between the ends of the inner liner 2|0 and if desired this end part may be riveted or welded or otherwise anchored, to the liner. The ribbon is then wound on shell MI by turning the winding hub and it should be noted that the ribbon is initially wound at the thin portion of the liner so that the second layer will rest on a substantially true cylindrical surface. During the winding any desired tension may be placed upon the ribbon 203 so that the coiled form between the shells will be more or less compact, as desired. As the space between the shells is filled with the coiled ribbon the ribbon will compress the inner shell 20| and expand the outer shell 202 a slight amount and this contraction and expansion will maintain substantial compression on the coil throughout the use of the mounting unit. When the space between the shells has been filled with the ribbon so that it forms a compact body, it is severed at the slot in the outer shell and drawn entirely within the shell. When the slot is formed by the tongue 2| I, the tongue is then forced downwardly to conform with the periphery of the outer shell. The outer end of the ribbon may then be firmly attached to the adjacent liner or shell by any suitable method such as brazing or welding. It may be desirable, however, to attach the strip or ribbon to the liners by an' adhesive which would obviate the application of appreciable heat to the parts which might affect the temper thereof. The liner 2| I must be mounted so that the space between its adjacent ends is in registration with the slot in shell 202 and the thin end of the liner extends along the ribbon entering between the shells. The liner 2| I thus provides a surface which engagessubstantially the entire periphery of the coil 203 and provides a uniform support for the coil. By this method of constructing the unit the compression on the coiled ribbon will firmly maintain the components in a unitary structure which may then be handled as a. unit. The shells are then machined to the precise inside and outside diameters of the unit for installation of a bearinng in its housing, as is indicated in broken lines in Fig. 24. Another feature of this method of fabrication is that it is not necessary to predetermine the precise length of ribbon to be used in each unit nor to provide precise outside and inside diameters of the inner and outer shells, respectively.

One model of a bearing mounting unit made in accordance with the preceding described method consisted of an inner shell having an outside diameter of approximately 8 and the inside diameter of the outer shell was approximately; 9 The ribbon was of high carbon blue steel, .010" thick, 2 wide and there were thirteen co 'nvolutions in the coil. The ribbon was coated with a thin film of graphite for lubrication betwen the laminations of the coil. The inner shell was turned on a spindle driven by a worm gear reduction drive having a 16 to 1 ratio and being driven manually by a crank having a two-foot throw. The coil was drawn as tightly as it could be manually with the power reducer described. In test. the radial load of 8000 lbs. caused a. deflection of .002" and an axial thrust of only 625 lbs. caused an axial displacement of .032" between the inner and outer shells.

The foregoing invention in its simplest form provides a means for taking up slight radial irregularities of assembly or manufacture or operation, permitting a still great r amo nt of ax al movement or freedom between the bearing and its housing and of equalizing the load over the parts or elements of a bearing. In use with two or more bearinngsthe invention has t e same pronerties as those above described with the additional pronertv of evenly distributing theload between several indi idual bearin s con tituting a combination or entire assembly interposed between theshaft and the housing in which it is carried. The invention obviously has an extremely wide range of cap city since there is little or no radial deflection under varying loads and the axial yield in the coil inter osed between bearing and hou ing can be varied within wide axial limits by the select on of various materials having in turn various s rface coatings, by the ti htness of the winding of the coil, by the number of convolutions in the coil, b its width with respect to the dimensions of t e bearing and by the lubrication supplied between the convolutions of the coil. and can. in fact. be so made as to provide a very considerable axial yield between bea in and ousing.

While I have h re shown cvlindrical, that is, sleeve type cf b arings, ball bearings and rol er bearings of certa n constructions, it will be readily understood t at the re ent invention is applicable to practically all ty es of bearings now in use to secure the results a ready described and is also easily adapt d to v rious combinations of bea in s and assemblies for various purpo es.

The materia of which the coil is form d in the present inv ntion will. of course, be determined by the particul r nature of the service in the assembly for which the coil is designed and in most cases will be formed of a metal stri of high ten i e strength either coated or uncoated but obv ously may, particularly for light service, be formed of other m terials such, for exam le, as a synthetic resin, having the hard substantially incompres ible nature. This may in fact be any materi l having the reouired tensi e, compression, frictional and fatig e characteristics recuired for the service for which it is intended. The thickness of the strip may vary according to the s ace requirements so th t a plurality of laminations can be provided which will gain the desired axial movement between the bearing and its support. In the descriptionof the invention,

10 the coiled strip has been referred to as a ribbon, but it is to be understood that in some cases the strip may be relatively rigid and therefore possess less of the characteristics of a ribbon.

Other means of employing the principle of the invention may be employed instead of the means explained, change being made as regards to the structure herein disclosed, provided the means stated by the following claims or the equivalent of such stated means be employed.

I, therefore, particularly point out and claim as my invention:

1. A hearing mounting structure comprising a support member and a cylindrical bearing member, one of said members being disposed within the other and spaced therefrom, and a body compactly interposed between said members and comprising at least one spirally wound coil of substantially incompressible material having adjacent surfaces of the convolutions in contact and arranged with said surfaces extending parallel to the axis of the bearing and being displaceable relative to one another axially of the bearing member, whereby substantially all radial movement between the support and bearing member is prevented.

2. A hearing mounting structure comprising a support member and a cylindrical bearing member, one of said members being disposed within the other and spaced therefrom, and a body compactly interposed between said members and comprising at least one spirally wound metallic coil having adjacent surfaces of the convolutions in contact and arranged with said surfaces extending parallel to the axis of the bearing and being displaceable relative to one another axially of the bearing member, whereby substantially all radial movement between the support and hearing member is prevented.

3. A bearing assembly comprising inner and outer concentric races containing rolling elements therebetween whereby one race may freely rotate relative to the other, a cylindrical housing surrounding the outer race and a body compactly interposed between said housing and outer race, said body comprising a spirally wound piece of substantially incompressible strip material having adjacent surfaces of the convolutions in contact and arranged substantially circumferentially of said races and being displaceable relative to one another axially of the races, said material being sufficiently hard to permit relative sliding of the layers axially of the races and to prevent substantially all radial movement between the outer race and housing.

4. A bearing mounting structure comprising inner and, outer annular members spaced from one another and two tightly wound coils of substantially incompressible strip material compactly interposed between said members and with the two coils wound in opposite directions, the adjacent surfaces of the convolutions of the coils being in contact, said contacting surfaces extending parallel to the axis of the bearing and being displaceable relative to one another axially of the bearing member whereby substantially all radial movement between the inner and outer member is prevented.

5. A bearing mounting structure comprising a support member and a cylindrical bearing member, one of said members being disposed within the other and spaced therefrom, and a body compactly interposed between said members and comprising at least one spirally wound coil. of substh ltially incompressible material having adjacent surfaces of the convolutions in contact and arranged with said surfaces extending parallel to the axis of the bearing and being displaceable relative to one another axially oi the bearing member whereby substantially all radial movement between the support member is prevented, and retaining means extending between the supportand bearing member for retaining said coil between the support and bearing member.

6. A hearing mounting element comprising a coil of relatively thin, flexible substantially incompressible material having adjacent surfaces of the convolutions in contact, being displaceable axially relative to one another and having exterior convolutions secured together as well as its interior convolutions also secured together and having the intermediate convolutions unsecured, whereby said exterior and interior convolutions form inner and outer collars between which the remaining convolutions lie and whereby substan- 20 tially all radial movement between the collars is prevented. t

7. A bearing mounting element comprising an internal supporting member and a substantially incompressible coil of relatively thin, flexible material surrounding the internal member and having adjacent surfaces of the convolutions in contact and being displaceable relative to one another axially and having exterior convolutions secured together while said remaining convolutions are unsecured one to another, whereby said exterior convolutions form an outer collar and whereby substantially all radial movement bel2 tween the collar and supporting member is prevented.

8. A bearing mounting element comprising an exterior collar and a substantially incompressible coil of relatively thin, flexible material within said collar and having adjacent surfaces of the convolutions in contact and being dlsplaceable axially relative to one another, said coil having its interior convolutions secured together to form an interior supporting member for the remaining convolutions, whereby substantially 'all radial movement between the collar and supporting member is prevented.

WALTER J. PARKS.

REFERENCES CITED The following references are of record in the file 01' this patent:

UNITED STATES PATENTS Number Name Date 1,127,657 McCormick Feb. 9, 1915 2,015,784 Brown Oct. 1, 1935 2,327,035 Gray Aug. 17, 1943 25 2,352,908 Moore July 4, 1944 2,377,681 Etchells June 5, 1945 2,403,645 Etchells July 9, 1946 FOREIGN PATENTS a Number Country Date 144,696 Switzerland Apr. 1, 1931 786,485 France Sept. 3, 1935 241,256 Switzerland June 17, 1946 

